Apparatus for applying abrasive to grinding apparatus



Aug. 17 1926. flfigggg 1 H. K. HITCHCOCK APPARATUS FOR APPLYING ABRASIVE T0 GRINDING APPARATUS Filed Jan, 22, 1924 4 SheetsSheetl FIE.1.. 2/ 28 ZZZ Aug. 17,1926. 1,596,658

H. K. HITCHCOCK APPARATUS FOR APPLYING ABRA SIVE TO GRINDING APPARATUS Filed Jan, 22, 1924 4 Sh.eetsSheet 2 m/swath;

Aug. 17 ,1926.

. 1,596,658 H. K. HITCHCOCK APPARATUS FOR APPLYING ABRASIVE T0 GRINDfNG APPkRnTUS Filed Jan. 22,- 1924 4 Sheets-Sheet 3 ("H In iv. MWI

Aug. 17 1926.

. 1,596,658 H. K. HlTCHCOCK APPARATUS FOR APPLYING ABRASIVE TO GRINDING, APPARATU Filed Jan. 1924 4 Sheets-sheaf;

FIE.5.

FIG

F'IG.E

Patented Aug. 17, 1926.

HALBERT K. I-II'ICHCOCK', OE PHITSIBTill-1GH,i PENNSYLVANIA.

ABPARATLUSuEORTABPLYEN G ABLE-naive 'io.eainnrndnrranarns;

A plication. filed January. 22-, "1924.. QSeri al 1%.. 81,702.] 7

The inventionre-lates to anapparatusior handling, grailing; and. applying, abrasive, such as sand, to grinding apparatudfand particularly.tosuchan, apparatus for use in connection witha straight. away operation for surfacingssheet.glass, marble. orthe like, I

'j ects the provision of. an improved apparatus for accomplishing tlielfunct-ion asahove set. forth, wherein: the density of the mixture 01"" abrasive and vater, in the graoingtank is automatically maintained. constant throughout, as Well. asthe upwardqvelocity ot the upward flow through the. -tanl vhich gives the grading etl'eet, thus. insuring that the degreeotfineness otthetgradeat each level and the .proportionof abrasive towater shall remain. correspondingly constant, and further, 7 the provision of. an. apparatus of very. simple, ",reliahle. Construction Briefly: stated, the apparatus, in. its. pretered form, ineludesaconical. grading tank supplied with, a mixture of sand and water at its lower. end hy. means lot. a. motor opentil ed: pu1np,-. which Withdraws the: mixture from a. sump; to. which the. drainage. from the various grinding machines is..returned'; a motor. operated device. for: feeding sand tothe. sump gautomatixe means governed by the density or. the. mixture in the. .tank for regulating the 1 feed of-the. sand; and. other automatic means.- governed! by the. amount 0t liquid. overflowing; from. the tank for regulating: the speed of operation. of the pump. The two. automatic. controlling means serveto maintain. the proportion ot' Water. to, abrasive constant; (which. propore tion can hemade. the one, to give the highest e-tfic-ieneyt; 1n. grinding) and to, maintain. a

eonstanti upward velocity. in: the, tank, so

that. the degree of fineness of the variousggradestaken from-the various levels. is maintained constant. The two controlling means are. also preferably. so correlated that, when the overflow from-the. tank, is

stopped entirely as. by the stoppageof the ump, the ieedina ot the sand is-autoinatically stoppech. The apparatus asherein set forth, While constitutingthe. preferred em V bodiment ofthje' invention, is merely illustrative of such invention inthe hroad form. as various other arrangements of controlling means might he'eniployed Without depart? ing from the invention. Such preferred form otapparatus is "shown in the. accompanyingdrau ings wherein:

Figure 1 is a.- vertical section taken through the'apparatus, Fig. 1 is anenlarged' detail section.- Fig. 2 is a partial plan view ottheapparatus. "Eig. 3 is aseetionion therliue III III" of Fig. 1. i Fig. l is a .seetiQn through ainodification. Fig.5.

is a 'sectionon tlieil ine V V ofFig. 4c; Fig-.

6 isla partial end 'vieiv'fl And Fig. 7 is a" partialside view on an enlarged scale.

Referring first: to the} general arrangen ent ftheprincipal parts of; the apparatus maybeenumerated. as follows 1' is a; conical grading tank supplied with a mixture of abrasive.andwat'er: from the drainage sump 2 otitliexgiji'iding machines by means ot-the rotarypump 3, which Sump provided withfa, suitable overflow passage (not shown),; 4. 5, 6,'- etc. are a series ofoutlet pipes. leading from. different levels. in the grader for.carryingab1 asive of different dc? giees.-. ot' fineness, to, the various grinding units; 7is, avariable speedelectric motor which drives the .pump 3,; 9'is. a sand hopper supplied from the chute. 10, inlthelo'ottom .ot 'Which is I a screw 11 for feeding the sand'to. the sump 2; -12jis. avariable speed electric motor for dij'iving thej screw 11 through the reducing gearing in the casing 13; 14. is,al1not0rfstarter for the motor 12 of ordinary commercial. type, which is stopped;andfstarted'lfby means of the push buttons. 15 v and 16;; 17 isv a nianuall'y open atedfrheostat iorthe fieldof the motor '12;

1.8 is. an automatic device for stopping and starting the/motor 12 through the motor 7 starter"; 19; is "a. device controlled by. the den: sity ofjtlie mixture inthetankl for. govern-ing. the. speed of, the sand feeding motor 12; 2O isf-apressurerheostatlying in the circuitoflthef field of'tlie motor; 12 and cone operated by the tube 19.; .21. andj2 2 are bells cont-tolled tromihe electroemagnetic operating device. 28 for indicating 'thestopping and starting. of the motor. 12 g 24: is any overflow?v trough .25 an overflow pipe; 26 is. a receptacle for receiving the overflow trollihgtlie speed thereof, whichdev-ice. is

mounted so that its weight with that of the water contained therein governs the pressure rheostat 27, which rheostat is located in the circuit of the field of the pump motor 7 28 is a limit switch which operates to secure the stoppage of the sand feeding motor 12 when the operation-of the pump 3 stops; 29 is a starter for the motor 7 governed from the push button switch box 30; and

31 is a manually operated rheostat in the circuit of the field of the motor 7.

The operation of the'pump 3 which pumps the mixture of abrasive and water up into V the tank 1 from the sump 2 is controlled by the overflow through the pipe 25. This pipe leads into the receptacle 26 having outlet 32 at its lower end.[ The relative amount of water flowing into the receptacle through the pipe 25 and out of the recep tacle through the pipe 32 governs the quantity of water which is retained by the receptacle and therefore its weight. This receptacle is pivotally supportedon a lever 33 fulcrumedlupon a suitable bracket 34 as indicated at 35 and provided with a counter held of the motor 7'which operates the pump 3. As the speed of operation of the pump increases, or the amount. of liquid withdrawn through the pipes 4, 5, 6,.etc.

decreases, the overflow of the tank will increase, thus tending toraise the level of the liquid in the receptacle 26. This increases the pressure on the rheostat 27, so that'the flow of current through the motor field is increased and the speed of the motor corre spondingly decreased. The reverse occurs when the overflow isreduced, in which case the level in'the receptacle 26is lowered, the

conductivity of the rheostat is reduced and the motor speeds up. The motor is in this way automatically controlled so thattheupward velocity of the abrasive andwater through the tank 1 is maintained constant, thus insuring that thefineness of theabrasive at any particular level is maintained constant. The pipe 25- is preferably'closed at its lower end as indicated in Fig. 1*. and

provided with the perforations 25 sothat the inertia of the water's flowing down through the pipe is not'applied to the receptacle 26 so that the'operation of the device is not subject to disturbance incident to this factorj A- uniform grinding effect is thus secured by each of the machines fed from one of the pipes at, 5, 6, etc. "The receptacle is guided and maintained in a true vertical plane I by use of an additional lever 39 pivoted atone end to the bracket 3% and at its other end to the receptacle. By proportioning the parts of the lever arm so that the arm to the left of the fulcrum 35 is rela tively short as compared withthe other arm, the device is made very responsive to changes of weight in the receptacle 36, so that the regulation secured is sensitive and accurate. This also applies to the lever42, later referred to which operatesthe rheostat 20. i

A device operating upon a similar principle and including a pressure rheostat is also employed to automatically control the density of the mixturein the tank 1 so that the proportion of water tosand is mainta ned constant. In this .ClGVlCG a vertical tube 19 is employed, open at both ends, and having the enlargen'ient 40 at its upper end. This tube is pivoted for vertical movement upon the bracket 41 by means of the lever ,42 and thelink 43, and the lever 42 bears at {H.upon thefplunger of the pressure rheostat 20 similar in construction to the rheostat heretofore described. This rh'eostat'lies in the circuit of the field of the motor 12, such circuit including the connections 45 and 46. As the density of the mixture in the tank 1 increases, t he. distance which the column of water is forced up in the enlargement 10 above the level of the liquid in the tank increases, thus applying the pressure'to the rheostat and decreasing the speed of rotation of the motor 12 so that the quantity of sand fed by the wormll is reduced. The

reverse occurs. when the'density of the mixture'decreases and the level of the liquid in the enlargement 4O moves'down, as in such case the pressure on the rheostat is reduced, thus increasing the resistance in the motor field circuit and causing the motor to speed up, The liquid in the tube 19 and its extension 4&0 rises above the level of that in the tank since the tube contains clear water which is less dense than the mixture surrounding the lower end of the tube. Any abrasive which enters the lower end of the tube immediately settles out so that. the hdensity of the liquid is less in the tube ithanoutside'of thefltube and the height of the'column of liquid supported correspondingly greater. The density of the mixture in the tank is in this manner-controlled and maintained constant. The tube 19 with its enlargement 4:0 is so arranged that the lower end 40 of such enlargement is always in the liquidof the tank, so that in all its positions it is subject tosubstantially the same buoyant reaction, and as a result there is no abrupt departure from the uniform variation in weight depending upon the height of "the column in the enlargement such as would be the c ase'if, in the operation of the mes es V 3 apparatus, the level o'f the liquid in the tank fell below thebottom 40 of the enlargement.

If, for any reason, the density in the tank is reduced beyond a predetermined point, a device-is provided for ringing the bell 21 and calling attention to this condition. This device includes an electro-magnet winding 47 which swings the bar 48 to the left againstthe resistance of the spring 49 when the flow through the winding is '1ncreased beyond a certain point. This move ment causes the bar. to contact. with the screw 50 so that a circuit through the bell 21 is completed from the battery 51 and the bellisrung. On the other hand, when the density of the mixture is increasedbeyond a certain point, the flow throughthe" circuit 45, 46 is increased, thus reducing the iiow through the shunt coil 47, so that the'spring 49' moves the bar 48 into contact with the screw 52, thus providing a: circuit through thebel 22 which rings, thus calling attention to the existing condition.

Provision is also made for automatically stopping the motor 12 in case the density of the mixture in the tank becomes too This-device comprises the swing-ing bar whiclrisoperated by the coil 54.- which is ar- 7 ranged in shunt with respect'to the field'circuit'. W hen the density of the liquid increases beyond certain point and the resistance inthe field circuit iscorrespondingly reduced, less current passes. through the COll M and the spring 55 moves the bar 90 to the right so that the spring contact arm 56 moves away fi'omthe arm 57, thus break ing the circuitthrough the wires 5'7, 58 which lead to the operating coil of the'motor starter 1a. As soon as this circuit is broken, the spring in theniotor starter opens the switch, thus stopping the motor. In

order to startthe motor after it has once been stopped, it is necessary to press in the starting push button 15.

An arrangement is also provided operating in conjunction with the mechanism just described for breaking the circuit through the wires 57, 58 and stopping the sand teed motor 1.2 when the pump 3is, for any reason,

stopped, or if the supply of liquid to-or from the pump should be interrupted, This device comprises the limit switch 28. which lies in the circuit 57,158. This switch is providedwith an 'arni 59 carrying a roller which engages the end of the" lever 33. When the receptacle 26 becoines'emptied or nearly emptied, thecounterweight on the lever 33 carries the letthand' end there-oi": downward below the roller on the switch lever so that such lever swings upward under the influenceofa spring and break the circuit through-the wires 57, 58, thus breaking the motor circuitin the starter 1%,

as heretofore described, andcausing the stop.-

the top of the tank by means ofthefiexible member 61, oi rubber or-other waterproof:

material'and this-ring is itself leveledup by means ofthebolts 62 extending throughthe top of the tank. In this manner, the upper edge oi the angle may readily. brought to a true vertical plane throughout the circumference oi? the tank. It is desirable to have the overflow around the entire perimeter of the tank as this secures a maximum discharge otthe liquid in thetank to the pipe 25 per unit of time, as the level in the tank rises, so that the control by the receptaole 26' acting through the rheostat s very rapid. The adjustment otthe operation of the pump is, therefore, sensitive andaccurater In order to maintain the level of the sump constant, a float 6&- is employed (Fig; 3)

which is connected to the bracket 65 by means off the lever 66 and link 67, the lever being secured at its other end to the gate valve 68. This gate. valve controls the supply oi"; water through the water main 69 so that from time totime, asthelevel of the sunip isreduced, .due to the fact that not'all 'ot the water usedinthegrinding operation is recovered, the valve is opened and an additional supply ot'water flows into the sump,

En case the operation of the pump is. dis

continued, the mixture in. the tank is prevented trom flowing back-into the sump by means of the. ball check valve 70 located in the lower end of the tankas indicatedin Fig. 1.

Figs. 4t, 5, and 6 illustrate a modification inso far as the method of supplying the sand to the sump is concerned. The grade itself, the pumpiand the means for controlling the operation or the pump by the overflow from the gradei' 'are the same as in the construction. heretofore described and the same numerals are used connection with both sets of apparatus. Themember 4-0, whose position is regulated by the density otthe mixture in the tank, and the pressurerheostat 2O operated therebv, are also thesame asiii the construction oi Figs. 1,2 and 3.. In the presentapparatus, the sand bin 71- may be located outside ofthe building so that it can i be readily supplied by means of an overhead crane or tel-fer, and the motor 7 2, which runs constanly, operates a valve 73 at the lower end of the sand bin or hopper instead oi op-- }erating'a screw feed as in the construction of '1. .The wear upon a feed of this kind 1S considerably less than is the case w th a screw edsuch as that of l. sand is conducted irom the bin to the sump 2'by means of a chute T l and preluiu nary to the deposit of the sand in the sump,

it is screened by means of the rotary screen 75. This screen is rotated by-meansof the belt 76 driven from the countershaft. 77, and the countershaft77 is in turn driven by means ofthe belt 78 from the shatt-79, thelatter shaft being driven by means of the belt 80 leading to the motor '72. A chute 81, open at thetop, extends into the screen and catches any gravel or the like, which collects therein, and which is carried by the movement of the screen. to a point where it can drop into the top of the chute from which it is removed or conducted away.

The valve 73 is mountedupon a shaft 82 and in opening is rotated in a clockwise direction as indicated by the arrow. The shaft 82 is provided with a depending arm 83 to which is secured the winding 0r coil 84 and this arm is swung to open the valve, when the winding is energized, by means of the arm 85 mounted loosely on the shaft 82, and provided with an armature 86 (Fig.

extending across the rear end of the magnet. The arm 85 1s oscillated continuously back and forth, 'but'is effective to swing the arm 83' keyed to the shaft 82 and open the valve, only when the winding is energized, so'that thetwo arms 85 and 83 are connected together. i The arm 85 is oscillated by means of the connecting rod-87 mountedupon a crank 88 carried by the shaft 79. The rod passes through a block 89, adjustable longitudinally of the arm 85 and provided with the pairs of nuts90 and 91 for adjusting the tension upon the spring 92, by means of which a yielding connection is provided be tween the rod 87 and the'arm 85. The valve shaft 82 also has keyed to it a third "arm 93 for operating the water valve 94 which controls the flow of water from the pipes 95 to the lower end of the sand bin. A spring 96 normally presses the arm upward to close the valve. When the arms 85 and 83 are magnetically connected together as heretofore described, to secure an operation of the valve 73, a correspondingoperation of the water valve 94 is secured,so that the water is admitted to the lower end of the sand binto assist in feeding the sand out whenever the valve is opened.

The energizing of the magnet winding 84 to secure a feed of sand tothe chute 74' is controll d by the pressure rheost-at, 20. This rheostat lies in a shunt circuit 97,398, connected with the main lines 99and 100 supplied with current from a suitable source. Also in shunt with the main lines 99 and 100 I is the circuit 101, 102, leading through the magnet winding 103. The-.winding controls the armature bar 104 normally held in open position by means of the spring 105. The two Comm rce and 107 which are connected when the bar 104 moves to theleft are connected to a circuit including the wires .108, 109 and 110 in whichthe winding 84 for controlling the valve'-'73- lies.

If the density of the mixture in the grader rises above a predetermined point, the carbon discs in the pressure rheostat are forced together, thus decreasing the resistance so that'more current passes through the circuit 97, 98 and correspondingly less current passes through the circuit including the magnet winding 103, so that the armature bar 104m0ves to the right' breaking the contact at' 106 and 107 so that the current through the winding 84 is discontinued. This disconnects the arms 85 and 83 so that the valve 73 is no longeroscillated and the feed of sand to the chute 74 is stopped. hen the density of the mixture in the tank 1 is' reduced, the reverse operation takes place, theflow of current through the Winding 103 increasing so that the armature bar closes the contacts 106 and 107 and the flow of current through the magnetwinding 84 occurs, thus connecting the arms 85 and 83 so that the valve 73 is oscillated back and forth permitting a flow of sand to the chute and at the same time the water valve 94 is periodically opened causing'a flow of water into the sand bin to loosen the sand. If the sand is frozen, warm water may be used" to facilitate the feed. e

The sand feeding arrangement is connect- .ed to the apparatus for controlling the speed of the pump 13 by'an arrangement similar to that described in connection with Fig. 1. In the present construction the limit switch 28 lies in the circuit 109., 110, in which the winding 84 lies so that if the pump should stopfland the lever 33 drop beyond a predetermined point,-the lever arm 59 is operated to break the circuit 109, 110 and cause themovement of the sand valve 73 to stop, the result beingthesame as referred to heretofore in connection with the first type of construction.

In order to indicate the status of the sand feed, means are provided for showing whetherthe density is too great Or toolittle by winding 113 for operating the armature bar 114 is employed, such winding lying in the circuit including the wires 115 and 116.

VVhen the densityof" the mixture in the tank rises above a'predetermined point and the flow of current through the circuit, including the rheostat-20 andthe wires 97 and 98, 1s increased, the flow through the winding 113 is correspondingly:decreasedand the spring 116 moves the armature'bar 114' so that it connects the contacts 117 and 118 and causes atlow of current through the filament of the lamp 112, so that a red light is secured at this point. When the density decreases, a reverse result is secured, an increased flow through the winding 113 being secured so that the armature bar swings to the left connectin g" the contacts v119 and 120 andsccuring a fiow current through (the filament of thel ip 111 w ich is provided with a 1 en in t is manner, the

densityorthe mixture is made visibly up parent to the operator, .andithe use or lights instead of bells as illustrated in the iii-st type (deconstruction is preterred as the lights indicate conditions even from a considerable distance while this is notthe case with .the bells, and furthermore, thenoise oi thebells ismore or less Objectionable.

What I claim is: I

T1. in combination, apparatus for supplying abrasiveto grinding mechanism comprising a grading tank arranged to discharge sunultaneously to sa d mechanism from dillerent le-velsm the tank, a pump for,

supplying a mixtureofabrasive and-water to the lower portion 01 the tank to provide.

a grading flow upward therethrough, and iieed means controlledby thedensity of the mixture in the tank for supplyingabrasive tosaid pump, said means including an up right tubeiin the tank, open at its lower end and having an enlargement at its upper end extending above the level of the water in the tank.

2. lncombination, apparatus for supplying for abrasive toflgrind ng ne'chamsm,

comprising a grading tank arranged .to discharge simultaneously to said mechanism from different levels in the tank, a pump for ,supplying a mixture of abrasive and water to the lower portion of thetank to provide -a grading flow upward therethrough, and feed means controlled by the density of the mixturein the tank for supplying abrasive to said pump, said means including an upright tube inthe tank, open at. its lower end and having an enlargement at its upper end extending above thelevel of the water in the tank and with its lower end adjacent such level. p

3. 111 combination, apparatus for supply ing abrasive xto grinding mechanism com prising a grading tank arranged to discharge simultaneously .to' said ime'chanis'm:

, atod -thereby.. i

4. In combination, apparatus for supply ing abrasive to grinding mechanism comprising a gradmg tank arranged to discharge simultaneouslyto said mechanism from diflferent'levels in tlie tank,;means for supplyingamixturepof abrasive and water to 'thef lower portion of the tank'to provide a grading. flow upward therethrough, abrasive .fee'dlng .means including an electric motor ior supplying 'ir'reshabrasive to said mixture, andimeansgoverned by the density ofjthe mixture in the tlankftorcontrolling saidieedlng means, said means includmg a. hydrometer lathe tank and a pressure rheostat operated thereby.

r f5 1n-.c.ombination, apparatus forsupply ing abrasive to grinding mechanism comprising a gra'dingptank arranged to dis charge .--s1multaneous ly to said ,Inechamsm from .difierent levels'inzthetank, means for supplyingnalmixture of abrasive and water to thelower portion of the tanlrntorprovide agrading flow upward therethrough, abra sive lfeeding means including an electric motor tor supplying ffresh abrasive to said mixture, and means, governed byrthe density otthe mixture in the gtankl for, controlling said ifeedingmeanapsa'id means including an uprighttubelinthetank, open at its ends 1 i i 90.

and. having an .enlarge1nent .atits upper end extending above the-level .o;t the water, and apressure rheostat operated thereby.

In combination, apparatus :for supplying abrasive to grinding mechanism comprising a grading tank arrangedgto discharge simultaneously to said mechanism, from dltterentxlevels in thetank, means for supplying a niixtureofabrasiveiand water to-thelower portion iof theetanlr to provide a grading fiow upward;therethrough, abrasive feeding :means including'an electric motor for supplying afresh abrasive to .said

mixture, and. means governed'by the density of the inlxture 1n the tank for controlling said feeding means said means including an uprighttube init'he tank, openat its ends andhaving an enlargement at its upper end extending above the level ofthe water, an abrasive" control valve, and .a pressure rheo stat operated by the tube and controlling said valve.

,7, 1ncombination, apparatus for supplying -abnasive Ito grinding imechanism Iconiprising "a grading .tank arranged to 'discharge slmultaneously to sald inecha-msm from different levelstherein, means for supplying .a mixture of abrasive and water to the tank to provide a grading g'flowthere through aioontainer for abrasive, an outlet valve, a 'icontinuously operating motor for opening -.land olosing the valve, areleasable connection between the valve-and motor, an

operating member positioned in the tank and governed :as "to v.theypressure which it exerts downwardly by the density of the mixture, and means-igoverned by said member- -wherebywsaid connection is --made and broken as the'density of the .inixture varies.

f 8. In combination, apparatus for supplyvabrasive to grinding mechanism com- 'iso prising, a grading tank arranged to discharge simultaneously to said mechanism tromdiflerent levels therein, means for sup; plying a mixture of abrasive and water to the tank to provide a grading flow therethrough, acontalner for 'abraslve, an outlet'valve, a continuously "operating motor tor'opening and closing the valve, an elec- ,tro-magnetic connection between the valve and motor, an operating circuit for sald' connection, an operating'member positioned in the tankand governed as to the pressure I which it exerts downwardly by the density of the mixture, and means governed by said member whereby said operating circuit is completed and broken as the density of the mixture varies.

" 9. In "combination,

prising a grading'tank arranged to 'd1scharge simultaneously to' said f mechanism from different levels therein, means :tor supplying a mixture of abrasive and water to the tank to provide a grading flow-therethrough, a container for abrasive, an out-c let valve, a'contlnuouslyoperating motor mixture, including an electric circuit and a pressure rheostat "whereby said operating circuit is completed and broken as thedensity of the mixture varies. 1

10. In combination, apparatus for supplying abrasive to grinding mechanism com prising a grading tank arranged to dis-:

charge simultaneously to said mechanism from different levels therein means for su plying a mixture of abrasive and water to the tank to provide a grading iiow therethrough, a container-for abrasive, an outlet va ve from the container, a water inlet connection to the container providedwith a valve, a continuously operating motor for opening and closing said valves, a releasable connection between the valves and the-motor, an operating member in-the tank andgoverned as to the pressure winch itexerts' downwardly by the density of the niix ture, and means governed by said mixturev whereby said connection is made and broken .as the density ofthe mixture variesj 11. In combinatlon, apparatus for supplying abrasive to grinding mechanism comprising a grading tank arranged to discharge trom different levels thereof to difterent units of said mechanism simultaneously, agpump torsupplying a mixture of abrasive andwater to the lower portion of the tank to provide agrading flow upward therethrough, a motor forthe pump and means governed by the overflow from thetank for-regulating the operation of said apparatus for supply ng abrasive 'to grindingmechanism com pump, said means comprising a receptacle -to which the overflow discharges provided with an'outlet, and a pressure rheostat governed by the weight of the water in the receptacle.

ing abrasive to grinding mechanism comprising a grading tank arranged to dis charge from diiferent levels thereof to different units of said mechanism simultaneously, a pump forsupplying a mixture of abrasive and water to the lower portion of the tank to provide a grading flow up ward therethrough, a motor for the pump and means governed by the overflow from the tank for regulating the operation of said. pump, said means comprising a receptacle to which "the overflow discharges provided with an outlet, and'a pressure rheostat in the field of the motor governed by the weight of the water in the receptacle and controlling said motor starter.

13. In combination, apparatus for supplying abrasiveto grinding mechanism comprising a grading tank arranged to dis: charge simultaneously to said mechanism from diil erent levels inthe tank, means for supplying a mixture of abrasive and water to the lower portion of the tank to provide a grading flow upward therethrough, an abrasive container, abrasive feeding means including a feed valve for the container, an electric motor for operating said valve, and a releasable connection between the motor and valve, and means governed by the den sity of the mixture in the tank for making and breaking said connection between the motor "and valve, said means including a hydrometer in the tank and a pressure rheostat'operatedthereby.

14'. In combination, apparatus for supplying abrasive to grinding mechanism comprising a grading tank arranged to discharge simultaneously to said mechanism" from difierentlevels in the tank, means for supplying a mixture of abrasive and water, to the lower portion ofthe tank to provide a grading fiow upward therethrough, an abrasive container, abrasive feedingmeans including a feed valve for the container, an electric motor operating said valve, and a releasable electric magnetic connection between the motor and valve, and means governed by the density of the mixture in the tank for controlling said connection, said means including an" upright tube in the tank, open at its ends and having 'an enlargement at it supper portion, and a pressure rheostat. I

15, In combination, apparatus for supplying abrasive to grinding mechanism com prising a grading tank arranged to discharge simultaneously to said mechanism from'difl'erent levels in the tank, means for' supplying a. mixture of abrasive and Water- 12. In combination, apparatus for supply- Inn 7 messes to the 1 lower A portion of 1 the tank to provide the density of the mixture in the tank for icontrolling said feeding m-eans, said means including an upright tube m the tank, open at "its ends and having -an' enlargement at 'its upper portion, --a motor starter, and a pressure :rheostat operated by the tube and lying in the circuit otthe field of thee-leetricwinotor tor-con trolling thespeed of the-motor and also ar ranged to stop'themotor.

16. In combinetion,-apparatus tor -supplying abrasive =to grinding unechanism comprising a grading tank arranged to dis charge-from different levelstheieotto different units or" said mechanismsimultaneously, a pump for supplying a. mixture of abrasive and Water tothe lower portion of the tank to I provide a grading flow upward therethrouglna motor for the pump and means governed by the ove flow tron hetank for regulating the operation of said pumpysaid means comprising a receptacle to which the overflow discharges provided with an outlet, and a ;pressure rheostat governed by the Weight of the water in the reeepaele, and

' lying in the oircuitot= the dieldot themotor.

t c-rent units ot saidgm-echanisi ously, 1 pump for supplying mitture of 17. In combination, apparatus for supplying abrasive to grindiirg "mechanism comprising a grading tank arranged to discharge "from different levels th veof to ditsiinultane' abrasive and Water to'the lowe'r. portion of thetank to provide a grading-no v upward tl'rerethrough, a motor for the "pump and tank for regulating the' 'operat-ion puinp,-=said meanscomprising-a receptat to which the overflow discharges provided with an-outlet, a motor starter, and sa pressure rheostat governed by'theweight ot the Water in the receptaele end controlling said motor StflTtQl,sfllCl rheos lyingin' the 'circuit of the field ot the motor.

18. In combination,apparatus tor supplying abrasive and Water to grinding mechanism, comprising a grading tank for said abrasive and water arranged to discharge to said mechani in from different levels, an abrasive container for supplying abrasive to said tank, means controlled by the density of the mixture in the tank for governing the supply of abrasive from said container to the tank, said means including an element in the tank which tends to vary with a change of level in the tank, means for producing in said tank an upward flow of the Water relative to the abrasive so as to separate the abrasive into grades, and means responsive to variations in the ratio taining the; sa

1 the" it said oftiow to discharge for automatically m n-- dratio substantially unite n.

119.?ln =cembinatien, apparatus forsupplying abrasive and :vmter :to grinding mechanism, comprising agra "igtank tor said/abrasive and water arranged to dis-- charge to said ineclranismtrom diii'erentle'w els an abrasive containerlor supplying ahra sive' to saidtank,.means centre led :by the density otthe mixturein the tank for governing the supply of abrasive from said con tainer to-the tan l means tor-producin said tankair-upward flow of the Water relative to the abrasivesoas to separate the abrasive into grades, means responsive to variations in the-ratio o1 flow to diseha g ge for automatically.maintaining the saidr tio uniform, and means governed by said ratios entirely cutting oil the supply of a nasive when such rate o'f ilou drops; determinedpoint, Y I i 20. 111 combination, apparatus for sup plying abrasive and Water to grinding mechanism, comprising a grading such abrasive and waterarranged charge to-said n ieehanism from oi els, means 'lor producing in said Ward flow of the liquid relative sive so as toseparate theabrasive'i 1 receiving means extendingaround he tank for receiving the overflowwhich passes the upper peripheral-edge of the tank, and

below a proover means governed by the amount of overlow to said receivin 'g means 'tor controllingsaid nateolf' flo-W upward-through the tank.

'21. In combination, apparatus tor sup-- plying abrasive and Water to grindi j n iechanism, comprising y a grading tank for said-abrasive-and Water arranged "to discharge to said mechanism "treni' ditl erent levels, means for producing in said an HPWEtI'tlflO-W of the liquid relative-to-the abrasive'so as to separate the abrasive into grades, receivingmeans Giltfiplu around the tank forreceivin'g the ovelloiv which passes over the upper peripheral e ge of the tankymeans "for leveling up said upper edge olfithe tank so that the overflow passing over sueh edge is substantiall uniform along the length thereof, and means governed by the amount of overflow to said receiving means for controlling said rate of flow up- Ward through the tank.

22. In combination, apparatus for supplying abrasive and Water to grinding mechanism, comprising a grading tanktor said abrasive and Water arranged to discharge to said mechanism from differentlevels, and

having an upper edge portion connected to in position to receive the overflow passing said upper edge portion, and means governed by the amount of overflow to said receiving means for controlling said rate. of flow upward through the tank.

23. In combination apparatus for supplying abrasive and water to grinding mechanism, comprising a grading tank for said abrasive and water arranged to. discharge to said mechanism from different levels, an abrasive container for supplying abrasive to said tank, motor driven means for insur-, ing a feed oi abrasive from sald contalner to the tank, a regulating device in the tank actuated by the density of the liquid, a rheostat operated thereby, and means governed by the rheostat for controlling said motor driven means.

24. In combination, apparatus for supply ing abrasive and water to grinding mechanism, comprising a container for abrasive and water for supplying the mixture to said mechanism, and feed means controlled by the density of the mixture in the container for supplying abrasive thereto, said 'mcans including an upright tube in the tank open at its lower end extending above the level of the mixture in the container.

25. In combination, apparatus for supply ing abrasive to grinding mechanism, comprising a container arranged to discharge to said mechanism, a container for abrasive, an outlet valve, a continuously operating motor for opening and closing the valve, a releasable connection between the valve and motor, an operating member positioned in the tank and governed as to the pressure-which it exerts by the density of the mixture, and

electrical control means governed by said member whereby said connection is made and broken depending upon sald density.

26. In combination, apparatus for supply-,

ing abrasive to grinding mechanism, comprising a container arranged to discharge to said mechanism, a container forabrasive, an outlet valve, a continuously operating motor for opening and closing the valve, a releasable connection between the valve and motor, an operating member positionedcin the tank and governed as to the pressure prising a container arranged to discharge to said mechanism, a container for abrasive, an outlet valve, a continuously operating motor for opening and closing the valve, a releasable electro-magnetic connection between the valve and' motor, an operating member positioned in the tank and governed as to the pressure which it exerts by the density of the mixture, and, electrical control means governed by said member whereby said connection is made and broken depending upon said density.

28. In combination, apparatus for supplying a mixture of abrasive and water to grinding mechanism comprising a container for said mixture adapted to, discharge to said'mechanism, an abrasive container for supplying abrasive tosaid first container,

motor driven means for securing a feed of abrasive from said abrasive container to said first container, a regulating device in said first container actuated by the density of said mixture, a rheostat operated thereby, and means governed by the rheostat for con trolling said motor driven means.

29. In combination, apparatus for supplying a mixture of abrasive and water to grinding mechanism comprising a container for said mixture adapted to discharge to said mechanism, an abrasive container for sup plying abrasive to said first container, motor driven means for securing a feed of abrasive from said abrasive container to said first container, a regulating device in said first container actuated by the density of said mixture, a pressure rheostat and a switch governed by the rheostat for controlling said motor driven means.

In testimony whereof, I have hereunto subscribed my name this 18th day of Jan, 1924.

- HALBERT K. HITCHCOCK. 

